Now the problem is that the system powers up but it doesn't actually boot up. It does absolutely nothing: no chime, no speaker beeps, no LED flashes. It just powers up, the HDD starts spinning, and the white LED lights up and stays there.

I have already removed all hardware: HDD, RAM, DVD. Nothing changes: the LED is ON and it doesn't flash twice to signal that the RAM is missing. According to the Power On Self-Test Beep Definition (https://support.apple.com/en-us/HT1547) from Apple, the Mac mini should beep once and its LED should flash twice when no RAM is installed. However, this doesn't happen.

The last thing that I could remove was the processor: I happened to have an Intel Pentium M 745 processor, which uses the same Socket 479 as the Mac mini, so I put it instead of the default one. The result is that the LED doesn't even light up! ... Well, I kind of expected that it would not work.

Next thing I tried was just powering the Mac mini without any processor installed. It just powers up and the white LED stays there... exactly the same as when the original processor is installed!

I'm now starting to get a bit tired of trying to revive this Mac, however after all the great information given in the first post I mentioned, I couldn't throw in the towel without first asking you guys: what other things should I try to revive this guy?

Thank you!

---- EDIT
I just thought that the RAM detection, and the beeping/flashing sequence, is a routine typically performed by the BIOS, right? Or in the case of Intel based Mac minis, the EFI. Could it be possible that this EFI got corrupted by some reason, and because of this no hardware initialization is being performed?

the pentium M CPU is electrically incompatible with the Core duo Socket M while it physically fits in the socket it wont work electrically and you risk blowing up the CPU and or Logic board... any socket M core solo core duo core 2 duo 667Mhz FSB CPU should work in that Mac mini. also have you tried an SMC reset?

Seems that simply disconnecting the power cord from the machine for longer than 15 seconds is enough for the SMC chip to reset. If that is the case, then for each and every test that I've performed the SMC chip was already reset, because between tests the Mac mini was always disconnected for whole minutes, while I was searching for information in the web.

I found also a small button on the logic board, which I suppose forces a SMC firmware reset. When pressed, the white LED on the Mac goes dark and then lights up steadily again, in what I assume is a hardware reboot cycle. I have pressed this button several times (around 4 or 5), both with the machine powered and disconnected from power. In the thread linked in my first post, there was someone who made the Mac boot up when he "PRYED off the button with a small flathead". I'll need a bit of help here with my English (not native), because I cannot get myself clear on whether he meant to remove the button from the PCB, or just force it to go to a "disconnect" position (the verb "Pry" seems to mean both things depending on context).

Also, there is some important info I realized: immediately after connecting the power cord the Mac mini powers up on its own, without having to hit the power button. I didn't know how a Mac mini was supposed to work, but now I found out that this shouldn't happen. Following what I read in the Apple forums, this could signal a malfunction or corrupted SMC, or even a malfunction SMC reset button. I'm going to investigate on this route.

On the other hand, is it possible that those capacitors that I removed are the reason for the machine not booting? As per the thread linked in my first post, they are 10uF caps which are part of the power circuit, so I'm guessing that they should have nothing to do with the booting process. But who knows...

P.S. I actually learned about the physically compatible but electrically incompatible topic some hours after the fact, so I won't try this again. Lesson learned.

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